In a typical communication system, for example, an analog cellular radiotelephone system, adjustment of the voice deviation level of a signal transmitted is not required. The average and maximum deviation levels of a signal that a typical transmitter may be expected to transmit is essentially known for a given system, and as such circuit component values (i.e., resistors, capacitors, etc.) that comprise the transmitter can be designed into the transmitter circuitry. Consequently, the transmittal need not be capable of automatic deviation adjustment.
However, as techniques are developed to increase subscriber capacity without increasing the amount of cellular radiotelephone hardware required, new techniques for voice modulation, and hence entire systems, also develop. For example, one such system is the Narrowband Advanced Mobile Phone System (NAMPS). In NAMPS, enhanced compression techniques are utilized to essentially compress the voice conversations of three subscribers into the bandwidth of a typical analog transmission (AMPS, for example). As such, the deviation level that each subscriber conversation undergoes is decreased in the narrowband mode (NAMPS) in relation to the typical deviation level the conversation would normally undergo in the wideband mode (AMPS).
It is both economical and efficient to use a single, dual-mode transmitter for both the narrowband mode and the wideband mode. However, to manually adjust the dual-mode transmitter between the narrowband mode and the wideband mode via potentiometers is very inconvenient. Since voice deviation level accuracy is critical for quality mobile phone usage, and access to dual-mode transmitters is limited once they are employed in a cellular radiotelephone system, manual adjustments between the wideband and narrowband modes is impractical.
Thus, a need exists for a dual-mode transmitter which automatically adjusts between wideband and narrowband modes of operation while compensating for various extremes of voice deviation levels to be transmitted.